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DTC codes / U05xx · Network communication / U0594

U0594Invalid Data Received From Hybrid/EV Powertrain Control Module

U0594 is a communication fault where the hybrid or electric vehicle powertrain control module is sending data that the receiving modules consider invalid or out of range. The computer has detected that the expected message content is missing, corrupted, or inconsistent with what other modules report, rather than simply losing the connection.

SystemNetwork
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyProfessional
AreaNetwork communication

Symptoms you may notice

  • Illumination of the check engine light or a dedicated hybrid system warning light
  • The vehicle may enter a reduced power or limp mode with limited acceleration
  • The hybrid system may fail to start or may shut down unexpectedly
  • Often no symptoms besides the warning light, especially if the fault is intermittent
  • Inconsistent or blank readings on the instrument cluster for hybrid battery state of charge or power flow
  • Possible stored codes in other modules indicating lost communication with the hybrid powertrain control module

Common causes, most likely first

  1. Corroded, loose, or damaged wiring or connectors in the hybrid controller area network (CAN) bus circuit
  2. A failing hybrid or electric powertrain control module due to internal faults or software corruption
  3. Low or unstable 12-volt battery voltage affecting module communication
  4. Aftermarket accessories or poor grounding causing electrical interference on the CAN bus
  5. A software calibration issue in the hybrid control module requiring a reflash or update
  6. Faulty CAN bus termination resistors or a shorted data line within the hybrid network

How to diagnose and fix it

  1. Perform a full scan of all modules to record all stored and pending codes, then clear codes and test-drive to see if U0594 returns
  2. Inspect and test the 12-volt battery and charging system, as low voltage is a common cause of communication faults
  3. Visually inspect the hybrid powertrain control module connectors and CAN bus wiring for corrosion, chafing, or loose pins
  4. Measure CAN bus resistance and voltage to check for proper termination and signal integrity
  5. Check for technical service bulletins (TSBs) or software updates for the hybrid control module and related modules
  6. If wiring and power supply are good, substitute a known-good hybrid control module or perform a module reprogramming as directed by the manufacturer
  7. After repairs, clear codes and verify that no communication faults return during a thorough road test

What U0594 Does Not Always Mean

  • A U0594 does not automatically condemn the hybrid powertrain control module; a weak 12-volt battery or a bad ground can corrupt CAN messages and trigger this code.
  • Intermittent U0594 codes often stem from aftermarket electronics plugged into the OBD-II port or added wiring that introduces noise onto the CAN bus.
  • Some vehicles set U0594 when the hybrid module is functioning correctly but another module on the network is sending conflicting data, so always check for codes in all modules.
  • A software calibration mismatch between the hybrid control module and other modules can set this code even when all hardware tests pass, making a reflash necessary.
  • Water intrusion into connectors near the hybrid battery or inverter is a frequently overlooked cause of invalid data from the hybrid control module.

Can I keep driving with U0594?

If the vehicle drives normally with only the warning light on, you can drive it cautiously to a repair shop, but avoid heavy acceleration or long trips. If the vehicle is in limp mode or the hybrid system shuts down, stop driving and have it towed to prevent unsafe conditions.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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